The present invention relates in general to gas sampling apparatus, and more particularly, to an oxygen sensing apparatus and associate system. The embodiments disclosed herein cover both a cold sampler or analyzer and a hot sampler. One of the features of the present invention relates to the self-cleaning aspect with which the sampling occurs.
Many process control and instrumentation systems require that a small sample of gas be extracted from the process for analysis. The analysis may take place in the immediate vicinity of the extraction location, or the gas may be transported considerable distances before the analysis takes place. In practice, problems often arise due to plugging of the system by ash, particulate, water, tar, creosote, carbon, and other residuals of the process. The most severe problems usually occur as a result of the combustion of dirty fuels such as tar, coal, residual oil, wood, or other biomass products. There are usually some residual unburned products either in particulate or vapor form. As these products are drawn into the sampling system, they deposit and/or condense forming a residual deposit which traps other particulates such as ash or dust. These deposits eventually build up and plug the apparatus. These deposits are also often of such a nature that they can not be blown out with an air blast, but must be mechanically removed. Thus, gas sampling systems tend to require high maintenance for most applications with the exception of those involving very clean environments. These systems require periodic cleanout for proper operation. Probably the worst residuals tend to be condensates such as tar and creosote which are not at all easily removed. Such residuals may be those from a combustion process.
Accordingly, one object of the present invention is to overcome the problem of the forming of residual deposits and provide a system that is a self-cleaning system for gas analyzers.
Another object of the present invention is to provide a gas sampling system that requires little maintenance especially in comparison with prior systems and, in particular, those associated with the combustion of dirty fuels. Again, the system of this invention is self-cleaning, thus, drastically reducing the maintenance required.